Dirt runners are devices that are used on street sweeping machines and the like. Dirt runners are typically mounted on some movable housing portion such that when a street sweeping machine is engaged with sweeping the pavement surface, the dirt runners can be lowered into sliding engagement with that pavement surface and thereby prevent dirt from escaping from under the machine and help guide the dirt along a predetermined path to a collection receptacle in the street sweeping machine.
A typical street sweeping machine might have a dust collection system whereby the dirt receptacle sits up on a bed of a truck, a suction system is provided and routed down through the bed of the truck. A brush rearwardly of the suction path is rotated so as to impel the dirt toward the suction opening, the suction pulling the dirt up into the dirt receptacle. Dirt runners are provided on lateral sides to guide the dirt along the desired path and improve the suction capability of the street sweeper.
The normal wear and tear on dirt runners is substantial due to the fact that there is down pressure exerted on the dirt runner against the pavement surface, the downward force being at least the weight of the dirt runner itself and the weight of the movable housing portion to which it is connected. The pavement surfaces which the dirt runners encounter is also very abrasive and irregular and, for this reason, it is preferable to have dirt runners equipped with hard wear resistant material on the surface that contacts the roadway. Usually, such a hard wear resistant material is in the form of a hard cemented metal carbide, such as tungsten carbide.
The dirt runners of the prior art are rigidly connected to a housing portion of the street sweepers, usually a movable housing portion such that the dirt sweepers may be raised or lowered when out of use or in use, respectively. The movable direction then is only in the vertical direction. The housing portion and the dirt runners being very rigid in lateral directions to the direction of travel of the dirt runners. The dirt runners, of course, are also very rigid in the direction of travel, also.
The problem that arises with dirt runners of the prior art is the serious and expensive damage that can occur to one of these street sweeping machines when encountering normal irregularities while enagaged with the pavement surface. The dirt runner by its nature is relatively narrow in width and, as it slides along the pavement surface with its downward pressure on it, it encounters cracks, crevices, or recesses in the pavement bed. Some of these recesses are made in the form of sewer grates with slotted surfaces and railroad track crossings with their attendant clearances in the road bed for the tracks.
If the street sweeping machine is traveling in a straight line as it encounters and passes these irregularities, no damage will occur. However, in practical experience, these obstructions are encountered during various maneuvers of the street sweeping machine. In turning, for instance, if the dirt runner becomes engaged with a grated sewer cover or drops into the clearances provided for railroad tracks at a railroad crossing, a severe lateral side force creates a bending movement on the dirt runner.
The dirt runners of the prior art are rigidly connected to and supported by a housing portion of the street sweeping machine and thereby this severe bending movement is transferred to the housing portion. The result, of course, ranges from a slight bending of the housing to a very pronounced bending of the housing, either of which may be enough to interfere with the rotary operation of the brushes of the sweeper or severely limit the suction system employed by the sweeper.
With the foregoing in mind, a primary object of the present invention is to provide dirt runners having a laterally flexible support between the dirt runner and the housing portion.
Another object of the present invention is to provide an arrangement whereby a greater life expectancy of the dirt runner may be anticipated before having to be returned for repairs or replaced.
Another object of the present invention is to eliminate the possibility of serious damage to the street sweepers housing section when the dirt runners encounter any of the above-listed damaging items during its maneuvers.
Another object of the present invention is to provide a newly designed dirt runner such that the dirt runner and flexible means of support may be substituted directly on standard street sweeping machines as they now exist without any costly or significant modification to the street sweeping machines in the field.